1. Field of the Invention
The present invention relates to an improved method, composition, package, and kit for colon evacuation and cleansing prior to colonoscopy, or in preparation for other medical, radiologic and/or surgical procedures.
2. Introduction
Deaths from colon cancer have been declining since the mid-1980's due to the widespread use of colonoscopy for both earlier detection of existing cancers, and removal of premalignant colon polyps detected by screening colonoscopy. As a result, the American Cancer Society recommends that all persons over 50 years of age undergo a screening colonoscopy every 10 years. An estimated 42 million Americans have not yet undergone this recommended screening colon examination to date. One reason patients avoid scheduling this very important examination is a reluctance to undergo the thorough bowel cleansing that is required before the examination. Anecdotal stories of the salty and disagreeable taste of the commercially available colon cleansing solutions patients are required to drink prior to the examination abound, and the palatability of these products are a major reason patients avoid scheduling this potentially life-saving examination.
In most medical or surgical procedures involving the colon, cleanliness is an important prerequisite for various reasons: i.e., in colonoscopy cleanliness is essential for a complete and accurate examination as retained stool or particulate matter can easily mask or hide polyps or flat cancers; and in colorectal surgery cleanliness is very important to facilitate a sterile operation. An ideal bowel cleanser would be effective, ensuring complete and accurate visualization of the colonic mucosa, safe for all patient groups, including those with diabetes or compromised renal function, acceptable to patients, and reasonably priced. A better tasting solution would be even more preferred.
3. Description of the Related Art
Many different methods have been utilized in the past to cleanse the bowel prior to medical or surgical procedures, including the use of various laxatives, enemas, suppositories and/or prolonged dietary manipulations. Large volumes of 0.9% saline solution or poorly absorbed saccharides such as mannitol or sorbitol were administered in the past, but significant absorption or loss of fluid and electrolytes as a result of ingesting these kinds of preparations sometimes resulted in serious complications in elderly debilitated patients or those with cardiopulmonary problems. The modern era of colon cleansing was heralded by Davis and Fordtran in 1980 with the development of osmotically-balanced large volume solutions where there was no net absorption or secretion of fluid or electrolytes. (Davis G L, Gastroenterology: 78:991-995, 1980).
Colon cleansing solutions may be contrasted on the basis of their osmotic balance, or tonicity. Osmolality is a measure of the number of dissolved particles in a fluid and is measured as mOsm/kg. Osmolality can be directly measured using standard laboratory techniques such as freezing point depression or calculated from knowledge of the individual dissociated ions present in the solution. The osmotic activity of human serum or plasma is measured in mOsm/liter and is referred to as osmolarity. Normal human serum osmolarity is around 285-295 mOsm/L. Tonicity refers to the osmotic pressure created by solutions of differing osmolalities on either side of a semi-permeable membrane. Based on tonicity, colon cleansing solutions can be classified as isotonic, hypertonic, or hypotonic. Isotonic solutions have an equal balance of impermeable molecules on either side of a semi-permeable membrane and thus are in balance with the vasculature of the intestine and do not lead to any net absorption or loss of fluid or electrolytes from the body. Hypertonic solutions contain a greater concentration of impermeable solutes than the surrounding fluid, and have the potential to draw fluid into the intestine, a process that can potentially dehydrate a patient and concentrate the serum electrolytes. Hypotonic solutions contain a lower concentration of impermeable solutes than the surrounding fluid and can lead to excess absorption of free water from within the intestine and undesirable dilution of the serum electrolytes. Each general category of colon cleansing solutions has advantages and disadvantages, but the sheer number of variations described in the prior art attest to the fact that an ideal formulation has yet to be created that is effective, safe, and well tolerated by a majority of patients.
Isotonic or balanced colon lavage solutions as originally described by Davis and Fordtran contain a combination of electrolytes and a water soluble, poorly absorbed solute, generally polyethylene glycol (“PEG”) that is in osmotic balance with the normal serum concentrations of electrolytes in the vasculature of the intestinal tract. PEG is a complex, non-absorbed, inert polymer of ethylene oxide that works by attracting and holding the water ingested with the lavage solution within the lumen of the intestine through osmotic effects. The quantity of PEG contained in these solutions is typically adjusted with the electrolytes so that the osmolality of the final solution approximates that of normal human serum, or around 285-295 mOsm/L. Standard PEG-containing formulations include the formulation GoLYTELY®, based on the formula originally proposed by Davis and Fordtran and commercialized by Braintree Laboratories of Braintree, Mass., and a more recent Braintree formulation NuLYTELY® based on the patent (WO/1987/000754) by Fordtran which omits the sodium sulfate in the formulation and increases the amount of PEG in the final solution to maintain isotonicity. Other known formulations with PEG include a formulation provided by Alaven Pharmaceutical, LLC (Marietta, Ga.) under the trademark TriLyte®, and a formulation produced by Schwarz Pharma AG (Monheim, Germany) under the name CoLyte™.
Colon cleansing is achieved by the consumption of large volumes of these solutions, but as the solutions are isotonic, they do not cause any net water gain or loss within the lumen of the intestine. As a result, patients do not experience dehydration or major fluid or electrolyte shifts when these solutions are consumed, and they have been proven to be safe even when used with patients with cardiopulmonary, kidney, or fluid volume problems. However, patients find consumption of these isotonic solutions difficult to complete. The salty and bitter taste that occurs as a result of the electrolytes that are part of these formulations contribute to the nausea, vomiting, and bloating that patients often experience when consuming this type of solution, and even when these side effects do not occur, patients often complain that consumption of such solutions is extremely unpleasant.
In one attempt to address these difficulties, Braintree Laboratory introduced HalfLYTELY®, based on U.S. Pat. No. 7,291,324 by Dennett et al., in which bisacodyl delayed release tablets (Dulcolax®) are administered several hours prior to the patient's consumption of the lavage solution. Dennett et al. claims that the volume of solution that has to be consumed can be decreased from four to two liters and still produce adequate cleansing.
A different isotonic formulation described in U.S. Pat. No. 5,274,001 by Borody incorporates ascorbic acid/or a salt of ascorbic acid as osmotically-active solutes, in addition to PEG and sodium sulfate. Brody et al. report that ascorbic acid in this formulation acts as an additional osmotic agent that allows one to decrease the amount of fluid that has to be consumed to three liters. This formulation has been sold in Australia under the trade name GlycoPrep C™ (Pharmatel LLC, Sydney, Australia) for several years.
Hypertonic colon cleansing formulations contain high concentrations of osmotically-active solutes that, when consumed, draw and retain large amounts of water from the patient's circulation into the lumen of the intestinal tract, which then distends the colon, stimulates peristalsis, and evacuates the contents of the colon. Whereas isotonic formulations incorporate the volume of required fluid as part of their formulae requiring two to four liters to do so, hypertonic solutions draw a large part of the required fluid from the patient. As a result, such formulations have the potential to cause sudden fluid and electrolyte shifts, dehydration, and concentration of the electrolytes in the serum, which can result in permanent kidney damage or even death in certain patients if preparations are consumed without ingestion of sufficient additional water.
An older hypertonic method of colon cleansing involved the ingestion of solutions that contained hypertonic concentrations of poorly absorbed, but potentially fermentable 6-carbon sugar alcohols such as mannitol or sorbitol. Reports of colonic explosion and death as a result of hydrogen and methane gases formed from the fermentation of these substances by the bacterial flora ignited by the electrocautery used at the time of polypectomy (Bigard M A, et al., Gastroenterology 77:1307-1310, 1979), led to a general consensus that simple or complex sugars should not be utilized in colon lavage solutions.
The most widely utilized hypertonic colon cleansing agents contain a concentrated aqueous solution of phosphate salts in liquid or tablet form (NaP), and therefore minimize the problems/complaints associated with large-volume PEG solutions. The C.B. Fleet Company (Lynchburg, Va.) manufactured and sold Fleet Phospho-Soda®, which is comprised of 480 gms/L of monobasic sodium phosphate and 180 gms/L of dibasic sodium phosphate. Randomized, controlled trials of this formulation were reported to demonstrate equivalent efficacy and superior tolerability solutions when compared with the larger volume PEG-containing solutions. (Barkun A., Can. J Gastroenterol. 20(11):699-710, 2006). However, this formulation had an extremely salty and unpleasant taste. In addition, the high concentration of phosphate salts in this type of formulation produced a large influx of fluid and electrolytes into the lumen of the intestine from the patient's circulation, resulting in problems with dehydration, metabolic derangement, kidney damage, and even some reported deaths which prompted the FDA to issue a safety warning on Fleet Phospho-soda. The C.B. Fleet Company has subsequently recalled this product from the market. Salix Pharmaceuticals, LLC (Morrisville, N.C.) continues to sell a tablet form of a sodium phosphate commercialized as Osmoprep® that carries a black box warning. Visicol® is another tablet preparation of NaP sold by InKine Pharmaceutical Company (now merged with Salix Pharmaceuticals, LLC).
U.S. Pat. No. 6,946,149 by Cleveland describes a smaller volume, hypertonic solution that avoids the adverse effects of the high sodium phosphate in prior art formulations by incorporating a mixture of sulfate salts (sodium, potassium, and magnesium sulfates) in place of phosphate salts in the formulation. In a later patent application, US 2009/0258090, Cleveland also incorporates 0.01%-0.1% by weight of an artificial sweetener from a group of chlorinated sucrose isomers that includes saccharin and/or Sucralose to this mixture of sulfate salts and PEG, and thereby lowers the perceived saltiness of the solution to the equivalent of about 0.2% to 2.6% sodium chloride in water. Braintree Laboratories has recently commercialized this formulation as Suprep®, and FDA approval was only recently granted for this product in August of 2010. Patients are required to consume 3 total liters of fluid when utilizing the Suprep® method of colon cleansing (1 liter of Suprep® in split-dose fashion with each 500 ml dose of Suprep® followed with 1 liter of water). Cleansing and completion results were the same when compared to Movieprep® or isotonic PEG-containing lavage solutions, but vomiting was slightly more common in the Suprep® group (DiPalma J A, Rodriguez R, McGown J, and Cleveland M., American Journal Gastroenterology, 104:2275-2284, 2010).
U.S. Pat. No. 7,169,381 by Barras describes a 2 liter hypertonic composition that contains ascorbic acid or salts of ascorbic acid, an alkali metal sulfate, and certain electrolytes in addition to PEG. Barras reports that this formulation is equal in efficacy to previous 3 or 4 liter compositions without requiring a preceding dose of bisacodyl (Dulcolax®). This composition has been commercialized and sold by Salix Pharmaceutical, LLC as Movieprep®. The sodium sulfate and ascorbic acid components in Movieprep®, however, still give the solution a salty lemon-lime taste that many patients find disagreeable, and nausea and vomiting of this preparation has also been noted. (See DiPalma reference above.)
A different type of colon cleansing solution has been described in Japanese Patent 2721929. This formulation incorporates the minimally-fermentable sugar alcohols xylitol and/or erythritol in a concentration of from 5.0-35.0 grams per liter as well as a corresponding amount of sodium and potassium electrolytes to maintain isotonicity. These sugar alcohols were specifically utilized in the composition to avoid the use of PEG in colon cleansing solutions. The lower concentrations of xylitol and/or erythritol claimed would require a concomitant increase in sodium sulfate and/or additional electrolytes to maintain isotonicity, at the cost of increasing the salty taste and decreasing the palatability of the final solution.
As a result of these multiple ongoing problems with the existing art, a growing number of physicians are utilizing a non-FDA approved hypotonic mixture of a proprietary PEG 3350 product Miralax® (Braintree Laboratory), mixed with a 2 liter volume of Gatorade® or other sports drink/rehydration solution as an electrolyte source (PEG-ELS). This colon cleansing solution is, on belief, better tasting (as it contains sugar and little salt), is inexpensive, and can be prepared by the patient from all over-the-counter products. Most sport drink/electrolyte solutions contain up to 6% carbohydrates, however, including high-fructose corn syrup which is believed to prompt several health problems, and particularly so in diabetic patients, as well as carry the risks of fermentation by the bacterial flora in the colon into potentially explosive hydrogen and methane gas. In addition, the relatively low concentration of electrolytes and dilute nature of these hypotonic formulas can lead to excess absorption of free water and result in significant fluid overload, hemodilution, and serious electrolyte imbalance, including low serum sodium levels (hyponatremia) which can cause swelling of the brain, confusion, seizures, and rarely, death. Despite these concerns, the non-FDA approved use of PEG-ELS continues to grow.
Therefore, there remains a need in the art for a colonic cleansing formulation that has the following advantages:                1) improves the quality of bowel cleansing prior to colonoscopy, surgery, or radiologic examinations;        2) provides improved taste to encourage patients to consume the entire preparation as prescribed;        3) is easy and convenient for patients to prepare;        4) avoids the risk of creating potentially explosive gases from bacterial fermentation of the solution;        5) does not impact insulin levels or raise blood sugar levels in diabetic patients; and        6) is safe.        